Thermodynamic Metrics Research Articles

Physics Models and Machine Learning in Molecular Dynamics

Abstract. Tackling the complexity of particle interactions, this investigation introduces a unified computational methodology employing Moldy, Gnuplot, and Visual Molecular Dynamics (VMD). Inspired by the n-body problem's persistent intrigue, specifically the three-body dynamics within molecular systems, we leverage Molecular Dynamics (MD) simulations to forecast and scrutinize the nuanced behavior of atomic and molecular entities. Moldy, a flexible MD software, facilitated the simulation of particle trajectories and interactions across diverse scenarios, with meticulous documentation of the resulting data. For visual analytics and insight extraction, Gnuplot crafted detailed plots depicting kinetic and potential energies alongside other thermodynamic metrics over temporal scales. The integration of VMD culminated in our analysis by vividly portraying the molecular motions, enhancing comprehension of emergent patterns. This study not only endorses Moldy's precision in MD simulations but also highlights the potent alliance among simulation, analysis, and visualization in elucidating intricate particle interactions. In summary, our work underscores the efficacy of the Moldy-Gnuplot-VMD triad as a formidable resource for scientists engaged in molecular motion prediction and analysis, paving fresh paths in computational physics and chemistry research.

Computational study on metal-free dye-sensitized solar cells utilizing heterocyclic derivative π-spacers with open and fused rings: Design and analysis of D-π-A-π-A dye sensitizers

A series of metal-free dye-sensitized solar cells featuring a D-π-A-π-A configuration is devised, employing various heterocyclic derivative π-spacers in both open and fused configurations. Employing DFT and TD-DFT methods, the optoelectronic and photovoltaic characteristics of the dye are scrutinized. To evaluate the impact of diverse heterocyclic spacers, structural parameters such as distance and dihedral angle, alongside thermodynamic metrics including electron injection efficiency (ΔGinject), regeneration efficiency (ΔGreg), light harvesting efficiency (LHE), open-circuit photovoltage (VOC), and short-circuit current density (JSC) are assessed. Results indicate that selected dyes with open and fused configurations of heterocyclic π-spacers such as O-CNC-2, O-CNN-4, O-NNC-7, O-NNN-8, F-NNC-2, and F-NNN-1 exhibited superior electron density distribution, higher ΔGinject, lower ΔGreg, elevated VOC, and JSC compared to their counterparts based on open configurations. These D-π-A-π-A dyes can emerge as promising candidates for future applications in solar cells.

Breaking a Molecular Scaling Relationship Using an Iron-Iron Fused Porphyrin Electrocatalyst for Oxygen Reduction.

The design of efficient electrocatalysts is limited by scaling relationships governing trade-offs between thermodynamic and kinetic performance metrics. This ″iron law″ of electrocatalysis arises from synthetic design strategies, where structural alterations to a catalyst must balance nucleophilic versus electrophilic character. Efforts to circumvent this fundamental impasse have focused on bioinspired applications of extended coordination spheres and charged sites proximal to a catalytic center. Herein, we report evidence for breaking a molecular scaling relationship involving electrocatalysis of the oxygen reduction reaction (ORR) by leveraging ligand design. We achieve this using a binuclear catalyst (a diiron porphyrin), featuring a macrocyclic ligand with extended electronic conjugation. This ligand motif delocalizes electrons across the molecular scaffold, improving the catalyst's nucleophilic and electrophilic character. As a result, our binuclear catalyst exhibits low overpotential and high catalytic turnover frequency, breaking the traditional trade-off between these two metrics.

Adsorption of Bromothymol Blue Dye onto Bauxite Clay

The goal of the current work is to use an inexpensive, non-toxic material with a high water absorption capacity, bauxite clay, to adsorb the bromothymol blue dye from an aqueous solution. In the production of textiles, leather, paint, food, cosmetics, and pharmaceuticals, synthetic organic compounds are used as dyes almost exclusively in modern industrial processes. Because to their harmful side effects, which include their inherent carcinogenicity, toxicity, and mutagenicity as well as the results of their biological transformation, these dyes pose a serious hazard to the environment when they are released. Clay minerals are valuable as depolluting agents due to their swelling potential, colloidal behavior, and adsorption capacity. The adsorption behavior of bromothymol blue dye from an aqueous solution was studied using bauxite clay. Different variables such as contact time, dosage, ionic strength, and temperature were studied to show the effect on bromothymol blue adsorption onto bauxite clay from an aqueous solution using the batch adsorption method. This study showed that the adsorption decreased by increasing the temperature (15–40 C) and increased by increasing the clay weight from 0.2 to 1.6 g. It also showed as the amount of time rose, the adsorption grew until it reached an equilibrium time of 155 minutes. Thermodynamic metrics including change in free energy (∆G), enthalpy (∆H), and entropy (∆S) all were assessed. A positive correlation was found between the absorbance and the range of concentrations of bromothymol blue (4–32 g/mL) with a correlation coefficient of 0.9911. The maximum wavelength was found and set to 432 nm for all measurements

Functional hierarchies in brain dynamics characterized by signal reversibility in ferret cortex.

Brain signal irreversibility has been shown to be a promising approach to study neural dynamics. Nevertheless, the relation with cortical hierarchy and the influence of different electrophysiological features is not completely understood. In this study, we recorded local field potentials (LFPs) during spontaneous behavior, including awake and sleep periods, using custom micro-electrocorticographic (μECoG) arrays implanted in ferrets. In contrast to humans, ferrets remain less time in each state across the sleep-wake cycle. We deployed a diverse set of metrics in order to measure the levels of complexity of the different behavioral states. In particular, brain irreversibility, which is a signature of non-equilibrium dynamics, captured by the arrow of time of the signal, revealed the hierarchical organization of the ferret's cortex. We found different signatures of irreversibility and functional hierarchy of large-scale dynamics in three different brain states (active awake, quiet awake, and deep sleep), showing a lower level of irreversibility in the deep sleep stage, compared to the other. Irreversibility also allowed us to disentangle the influence of different cortical areas and frequency bands in this process, showing a predominance of the parietal cortex and the theta band. Furthermore, when inspecting the embedded dynamic through a Hidden Markov Model, the deep sleep stage was revealed to have a lower switching rate and lower entropy production. These results suggest functional hierarchies in organization that can be revealed through thermodynamic features and information theory metrics.

Study on Microelectrochemical Inhomogeneity of an SA508-309L/308L Overlay Welded Joint.

The corrosion behavior of the dissimilar metal welded joint (DMWJ) is highly dependent on its heterogeneous microstructures. However, directly measuring the electrochemical properties of microstructures in different heat-affected zones (HAZs) is a formidable challenge, because traditional bulk electrochemistry can only offer an average signal. Herein, the microelectrochemical properties of an SA508-309L/308L DMWJ were measured in 3.5 wt % NaCl solution using lithography and capillary techniques. Specifically, high-throughput microelectrochemical tests, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP), were conducted on 168 spots (Φ 12 μm). Results revealed five typical EIS responses and seven varieties of PDP curves (different magnitudes of the current density). The maps of thermodynamic and kinetic metrics, such as polarization resistance derived from EIS, corrosion potentials, and corrosion currents extracted from potentiodynamic polarization curves, demonstrated good consistency. The uniform corrosion tendency of the SA508 HAZ subregions during the immersion tests is basically consistent with its Ecorr_avg order of subcritical HAZ (C5, -371 mV) < intercritical HAZ (C4, -546 mV) < fine-grained HAZ2 (C3, -579 mV) < fine-grained HAZ1 (C2, -593 mV). The random presence of inclusions leads to highly heterogeneous microelectrochemical properties of the DMWJ, thereby causing localized corrosion to occur preferentially. Moreover, the macroscopic corrosion behavior is affected by the corrosion products, which display a protective effect that modifies the local electrochemical activity of the SA508 HAZ. The combination of microelectrochemical properties allows for a more comprehensive understanding of the macroscopic corrosion behavior of metals and the galvanic effect between the heterogeneous microstructures.

Dealing with Aspects of Performance and Environmental Impact of Aircraft Engine with Thermodynamic Metrics

The limited energy source indicates the necessity of efficient energy consumption in every field of life. Especially, the prompt growth in aviation sector makes this issue more important. In this study, effects of power settings on several thermodynamic indicators regarding low by-pass turbofan engine (LBP-TFE) are investigated. For this aim, the energy and exergy analyses are implemented to the system of turbofan engine for eighteen operating points. According to performance analysis, thrust value of the LBP-TFE changes from 10.77 kN to 71.8 kN throughout RPM values. According to exergetic findings, relative exergy losses from Fan outlet decreases from 52.34 % to 30.58 % whereas exergy efficiency of the LBP-TFE increases from 10.9 % to 30.1 %. Considering improved exergy efficiency, it changes 25.03 % and 41.03 % at the same RPM intervals. As for environmental assessments, environmental effect factor (EEF) of LBP-TFE diminishes from 5.8 to 1.32 while ecological effect factor decreases from 9.16 to 3.31. Finally, specific irreversibility production of LBP-TFE decreases from 0.4811 MW/kN and 0.2716 MW/kN. Considering these outcomes, behaviour of the investigated metrics regarding main components is different from each other. Therefore, the results of these parameters calculated for the whole engine could help understanding optimum running point in terms of exergetic and environmental sustainability.

The feasibility of integrating three different thermal desalination units and a geothermal cycle combined with a modified Kalina cycle

To upsurge the geothermal energy-based freshwater production capacity, a novel waste heat recovery model for a geothermal cycle combined with a modified Kalina cycle is designed, investigated, and optimized in this study. The designed model relies on temperature control and efficient heat recovery capable of combining three different thermal desalination units, including multi-effect, humidification dehumidification, and separation vessel units. To ensure the possibility of integration, a coherent multi-aspect sensitivity study is conducted from thermodynamic and exergoeconomic points of view. In addition, two principal optimization scenarios are regarded and programmed in which total exergy destruction rate/output freshwater and net present value/fixed capital investment cases are included. To do optimization, a multi-objective grey wolf optimization algorithm is developed and utilized. According to the results of the sensitivity study, it is elicited that the variability of studied thermodynamic and cost-based metrics is more exposed to the variation in the inlet temperature of the separation vessel desalination. Besides, the first optimization scenario exhibits that the exergy destruction and freshwater production rates are gauged at 640.9kW and 0.619kg/s, correspondingly. Furthermore, in the second scenario, the net present value and fixed capital investment are obtained to be 164,638 $ and 225,653 $, respectively.

Contact and metric structures in black hole chemistry

We review recent studies of contact and thermodynamic geometry for black holes in AdS spacetimes in the extended thermodynamics framework. The cosmological constant gives rise to the notion of pressure P = −Λ/8π and, subsequently a conjugate volume V, thereby leading to a close analogy with hydrostatic thermodynamic systems. To begin with, we review the contact geometry approach to thermodynamics in general and then consider thermodynamic metrics constructed as the Hessians of various thermodynamic potentials. We then study their correspondence to statistical ensembles for systems with two-dimensional spaces of equilibrium states. From the zeroes and divergences of the curvature scalar obtained from the metric, we carefully analyze the issue of ensemble non-equivalence and show certain complimentary behaviors in the description of a thermodynamic system. Following a thorough analysis of the familiar van der Waals system, we turn our attention to black holes in extended phase space. Considering the example of charged AdS black holes, we discuss the generic features of their thermodynamic geometry in detail. The relationship of the thermodynamic curvature(s) with critical points as well as microscopic interactions in black holes is also briefly explored. We finally set up the thermodynamic geometry for finite temperature gauge theories dual to black holes in AdS via holographic correspondence and comment on recent progress.

Analysis of entropy production in finitely slow processes between nonequilibrium steady states.

We investigate entropy production in finitely slow transitions between nonequilibrium steady states in Markov jump processes using the improved adiabatic approximation method, which has a close relationship with the slow driving perturbation. This method provides systematic improvement of the adiabatic approximation on infinitely slow transitions from which we obtain nonadiabatic corrections. We analyze two types of excess entropy production and confirm that the leading adiabatic contribution reproduces known results, and then obtain nonadiabatic corrections written in terms of thermodynamic metrics defined in protocol parameter spaces. We also numerically study the resulting excess entropy production in a two-state system.

Phase boundaries and the Widom line from the Ruppeiner geometry of fluids.

The Ruppeiner geometry has been shown to provide novel ways for constructing the phase boundaries and the Widom line of certain fluids. This paper examines the applicability of these geometric constructions to more general fluids. We develop a general equation-of-state expansion for fluids near a critical point that mainly assumes analyticity with respect to the number density. Based on this general parametrization of fluids, we prove the equivalence of the Ruppeiner geometric construction and the standard Maxwell construction of phase boundaries near the critical point. In contrast, we find that the usual prescription based on the Ruppeiner geometry for the Widom line does not produce the expected Widom line for arbitrary cases of our general fluid equationof state. This usual prescription relies on the Ruppeiner metric induced on a particular hypersurface of the thermodynamic manifold. We show that by choosing a different hypersurface, which we call the Ruppeiner-N surface, and using its associated induced metric, the Ruppeiner construction generates the entire Widom line of the van der Waals fluid exactly, even away from the critical point. Interestingly, this alternative hypersurface yields another benefit. It improves the classification scheme originally proposed by Diósi etal. for partitioning the van der Waals state space into its different phases using geodesics of a thermodynamic metric. We argue that, whereas the original Diósi boundaries did not correspond to any clear thermodynamic lines, the corresponding boundaries based on the Ruppeiner-N metric become sensitive to the presence of the van der Waals Widom line and provide the correct classification of all van der Waals states. These results suggest that the Ruppeiner-N surface may be the more appropriate hypersurface to use when studying phase diagrams with thermodynamic geometry.

Evaluating and modelling of thermodynamic and environmental parameters of a gas turbine engine and its components

Nowadays, aero-engines have been opted more due to their important benefits for powering unmanned aerial vehicles or producing electricity or pneumatic powers for aircraft engines. In this study, a small gas turbine engine (S-GTE) used in aviation applications was dealt with using thermodynamic and environmental methods at ten different power settings (PSs) as well as different design variables involving turbine inlet temperature (TIT) ranging 1350 K and 1550 K and pressure ratio of compressor ranging 10 and 16. Thus, both effects of design variables and power settings on thermo-environmental metrics were investigated under different cases. Additionally, several parameters of the engine were modelled according to power settings which the engine operate. When considering performance findings, specific fuel consumption increases from 0.3262 kg/kWh to 1.2341 kg/kWh as shaft power decreases from 415 kW to 41.6 kW. According to thermodynamics computations, exergy efficiency of the combustor diminishes from 83.52% to 74.92% at baseline. Moreover, the higher TIT leads this metric to increase from 83.52% to 87.17%, whereas effect of CPR is not observed as important as the impact off TIT. However, exergy efficiency of the whole engine changes from 24.15% to 6.38% due to decrement in the PS. Moreover, the higher TIT and CPR of the engine favorably affect this metric. On the other hand, enviroeconomic cost factor (ECF) of the engine drops from 39.65 billion Euro/year to 14.98 billion Euro/year, but environmental effect factor increases 2.62 to 9.29 due to decreasing PS. Lastly, there is non-linear relationship between exergy efficiency and power setting, whereas enviroeconomic factor of the engine linearly changes with PSs. Namely, exergetic model is obtained with high accuracy as R2 of 0.995 at three-degree function while enviroeconomic cost factor model is achieved with high correctness as R2 of 0.9972 at first-degree function. These results show that modelling of thermodynamic metrics helps in understanding how extent these indicators pertinent to the engine are affected from power settings. Thus, optimum power setting without penalty on the engine performance could be discovered.

Modeling of performance and thermodynamic metrics of a conceptual turboprop engine by comparing different machine learning approaches

Modeling of performance and thermodynamic metrics of a conceptual turboprop engine by comparing different machine learning approaches

Optical characterization of stratified-premixed natural gas direct-injection combustion regimes.

Gaseous fuels for heavy-duty internal combustion engines provide inherent advantages for reducing CO2, particulate matter (PM), and NOX emissions. Pilot-ignited direct-injected NG (PIDING) combustion uses a small pilot injection of diesel to ignite a late-cycle main direct injection of NG, resulting in significant reduction of unburned CH4 emissions relative to port-injected NG. Previous works have identified NG premixing as a critical parameter establishing indicated efficiency and emissions performance. To this end, a recent experimental investigation using a metal engine identified six general regimes of PIDING heat release and emissions behavior arising from variation of NG stratification through control of relative injection timing (RIT) of the NG with respect to the pilot diesel. The objective of the current work is to provide comprehensive description of in-cylinder fuel mixing of direct injected gaseous fuel and its impacts on combustion and pollutant formation processes for stratified PIDING combustion. In-cylinder imaging of OH*-chemiluminescence (OH*-CL) and PM (700 nm), and measurement of local concentration of fuel is considered for 11 different , representing 5 regimes of stratified PIDING combustion (performed with MPa and ). The magnitude and cyclic variability of premixed fuel concentration near the bowl wall provides direct experimental validation of thermodynamic metrics ( , , ) that describe the fuel-air mixture state of all 5 regimes of PIDING combustion. The local fuel concentration develops non-monotonically and is a function of RIT. High indicated efficiency and low CH4 emissions previously observed for stratified-premixed PIDING combustion in previous (non-optical) investigations are due to: (i) very rapid reaction zone growth ( m/s) and (ii) more distributed early reaction zones when overlapping pilot and NG injections cause partial pilot quenching. These results connect and extend the findings of previous investigations and guide the future strategic implementation of NG stratification for improved combustion and emissions performance.

Thermodynamics of novel black holes in massive gravity coupled to nonlinear electrodynamics

By introducing a static and spherically symmetric geometry, we have solved the coupled electromagnetic and gravitational field equations in the presence of both, massive gravitons and nonlinear electrodynamics. The exact solutions show that massive gravity theory admits two novel classes of nonlinearly charged asymptotically AdS black holes. The black holes’ electric charge, mass, and other thermodynamic quantities have been calculated. Then, by use of a Smarr-type mass formula, it has been proved that the thermodynamical first law is valid for both the new massive black hole solutions. The black hole local stability has been investigated by use of the canonical ensemble and geometrical methods, separately. Through comparison of the results, we found that they are compatible provided that the HEPM or QII thermodynamic metrics are used. Global stability and Hawking–Page phase transition points have been studied by use of the grand canonical ensemble method and regarding the Gibbs free energy of the black holes.

Comparative study for air compression heat recovery based on organic Rankine cycle (ORC) in cryogenic air separation units

The annual energy consumption of the cryogenic air separation units (ASUs) reaches 205 TWh in China, over 80% of which is consumed in the compression processes while over 60% of the compression work is dissipated as waste heat. Efficient recovery and utilization of this amount of heat is expected to bring significant economic and environmental benefits. Organic Rankine cycle (ORC) based waste heat recovery systems for generating extra electricity or/and cooling the inlet air of the air compressors are proposed to achieve power saving and evaluated in terms of thermodynamic, economic and environmental metrics. These include an ORC-based electric generator (ORC-e) for extra electricity, an electrically coupled ORC and vapor compression refrigerator (ORC-e-VCR) and a mechanically coupled ORC and VCR (ORC-m-VCR) for extra electricity and compression power saving. A 60,000-Nm3/h scale cryogenic ASUs is selected for case studies and influence of the feed-air temperature and humidity is focused in the analyses. The results show that among these three systems, the ORC-m-VCR and ORC-e-VCR systems have similar performance when the expansion work-electricity conversion efficiency (ηe) is 90%, reaching the highest energy saving ratio of 11.7% and economic benefits with net present value achieving 154 million CNY. The ORC-m-VCR system outperforms the other two systems with ηe of 60% and 30%. This work presents comprehensive comparison of various heat recovery systems and provides practical guidance for configuration selection and design to achieve effective energy saving in air compression processes.

Thermodynamic, thermoenvironmental and thermoeconomic analyses of piston-prop engines (PPEs) for landing and take-off (LTO) flight phases

The four different piston-prop engines (PPE1, PPE2, PPE3, PPE4) are investigated along with thermodynamic (energy and exergy), thermoenvironmental (based on exergy), and thermoeconomic (economic, specific exergy cost [SPECO], exergy-cost-energy-mass [EXCEM], modified EXCEM [m-EXCEM]) analyses for Landing and Take-off (LTO) flight phases.Maximum power is generated by the engine in the take-off phase during flight time. The take-off phase is taken into account while comparing thermodynamic, thermoenvironmental and thermoeconomic performance metrics of engines since maximum fuel consumption happens and maximum engine power is realized in this phase. In this case, the specific fuel consumption, energy efficiency, exergy efficiency, environmental effect factor, ecological objective function, ecological impact points, specific product exergy cost, relative cost difference, exergoeconomic factor, waste exergy cost rate, EXCEM cost formation rate, and m-EXCEM cost formation rate of PPE3 are estimated to be 0.081 kg/MJ, 27.677%, 26.017%, 2.844, −1485.434 MJ/h, 2.897 mPts/MJ, 0.322 $/MJ, 430.263%, 33.908%, 139.120 $/h, 0.0141 MJ/h/$ and 2.453 MJ/$, respectively. The PPE3 is the best engine between the four different PPEs in the terms of thermodynamic efficiently, environmentally friendly, and cost-effective.

Thermodynamics of charged black holes with Maxwell and Born–Infeld fields in massive gravity theory

In the framework of massive gravity theory which is coupled to the Maxwell and Born–Infeld electrodynamics, we review derivation of the exact four-dimensional black hole solutions by use of a static and spherically symmetric geometry. The exact solutions are asymptotically AdS and show two-horizon, one-horizon, extreme and black holes without horizon. The Maxwell and Born–Infeld black hole solutions are compatible in the limit of large nonlinearity parameter and, both reduce to the Reissner–Nordström black hole in the absence of massive gravitons. By reviewing thermodynamic and conserved quantities, and making use of a Smarr-type mass formula, we check validity of the thermodynamical first law for both of Maxwell and Born–infeld black holes. We investigate thermal stability of the black holes by use of the canonical ensemble and geometrical approaches, separately. By calculating the specific heats and Ricci scalars of alternative thermodynamic metrics, we compare the results of geometrothermodynamics with those of canonical ensemble method. Also, we perform a global stability analysis by use of the grand canonical ensemble and noting the Gibbs free energy of the Maxwell and Born–Infeld black holes.

Optimal experimental design of physical property measurements for optimal chemical process simulations

Chemical process simulations depend on physical properties, which are usually available through property models with parameters estimated from experiments. The required experimental effort can be reduced using the method of Optimal Experimental Design (OED). OED reduces the number of experiments by minimising the expected uncertainty of the estimated parameters. In chemical engineering, however, the main purpose of an experiment is usually not to determine property parameters with minimum uncertainty but to simulate processes accurately. Therefore, this paper presents the OED of physical property measurements resulting in the most accurate process simulations: c-optimal experimental design (c-OED). c-OED aims to minimise the uncertainty of the process simulation results, which is estimated by linear uncertainty propagation from uncertain property parameters through the process model. We use c-OED to design liquid-liquid equilibrium and diffusion experiments minimising thermodynamic and economic performance metrics of three solvent-based processes. In all three case studies, the c-optimal design substantially reduces the experimental effort for the same simulation accuracy compared to state-of-the-art OED that neglects the process. Our findings are confirmed by a Monte-Carlo simulation of the designed experiments. Furthermore, we assess the limits of c-OED for highly nonlinear process models. Thus, the work shows how c-OED can successfully reduce experimental effort required for accurate process simulations by tailoring experimental designs to the process model.

Contact geometry and quantum thermodynamics of nanoscale steady states

We develop a geometric formalism suited for describing the quantum thermodynamics of a certain class of nanoscale systems (whose density matrix is expressible in the McLennan–Zubarev form) at any arbitrary non-equilibrium steady state. It is shown that the non-equilibrium steady states are points on control parameter spaces which are in a sense generated by the steady state Massieu–Planck function. By suitably altering the system’s boundary conditions, it is possible to take the system from one steady state to another. We provide a contact Hamiltonian description of such transformations and show that moving along the geodesics of the friction tensor results in a minimum increase of the free entropy along the transformation. The control parameter space is shown to be equipped with a natural Riemannian metric that is compatible with the contact structure of the quantum thermodynamic phase space which when expressed in a local coordinate chart, coincides with the Schlögl metric. Finally, we show that this metric is conformally related to other thermodynamic Hessian metrics which might be written on control parameter spaces. This provides various alternate ways of computing the Schlögl metric which is known to be equivalent to the Fisher information matrix.